Transcript Gustation/Olfaction/Auditory

Special Senses
• sensory receptors are within large, complex sensory
organs in the head
• smell in olfactory organs
connected
• taste in taste buds
• hearing and equilibrium in ears
• sight in eyes
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Sense of Smell
Olfactory Receptors
• chemoreceptors
• respond to chemicals dissolved in liquids
Olfactory Organs
• contain olfactory receptors and supporting epithelial
cells
• cover parts of nasal cavity, superior nasal conchae,
and a portion of the nasal septum
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Olfactory Receptors
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Olfactory Nerve Pathways
Once olfactory receptors are stimulated, nerve impulses
travel through
• olfactory nerves
olfactory bulbs
olfactory
tracts
limbic system (for emotions-mom’s apple
pie….) and olfactory cortex (for interpretation)
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Olfactory Stimulation
• olfactory organs located high in the nasal cavity
above the usual pathway of inhaled air
• olfactory receptors undergo sensory adaptation
rapidly
• sense of smell drops by 50% within a second after
stimulation
Olfactory Code
• hypothesis
• odor that is stimulated by a distinct set of receptor cells
and its associated receptor proteins (the variety stimulated
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determines the smell)
Sense of Taste
Taste Buds
• organs of taste
• located on papillae of tongue, roof of mouth, linings of
cheeks and walls of pharynx
Taste Receptors
• chemoreceptors
• taste cells – modified epithelial cells that function
as receptors
• taste hairs –microvilli that protrude from taste
cells; sensitive parts of taste cells
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Taste Receptors
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Taste Sensations
Four Primary Taste Sensations
• sweet – stimulated by carbohydrates
• sour – stimulated by acids
• salty – stimulated by salts
• bitter – stimulated by many organic compounds
Spicy foods activate pain receptors (and sour)
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Taste Nerve Pathways
Sensory impulses from taste receptors travel along
• cranial nerves to
• medulla oblongata to
• thalamus to
• gustatory cortex (for interpretation)
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Hearing
Ear – organ of hearing
Three Sections
• External
• Middle
• Inner
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External Ear
• auricle
• collects sounds waves
• external auditory meatus
• lined with ceruminous glands
• carries sound to tympanic
membrane
• terminates with tympanic
membrane
• tympanic membrane
• vibrates in response to sound
waves
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Middle Ear
• tympanic cavity
• air-filled space in temporal
bone
• auditory ossicles
• vibrate in response to tympanic
membrane
• malleus, incus, and stapes
• oval window
• opening in wall of tympanic
cavity
• stapes vibrates against it to
move fluids in inner ear
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Auditory Tube
• eustachian tube
• connects middle ear to
throat
• helps maintain equal
pressure on both sides
of tympanic membrane
(think altitude-pop)
• usually closed by
valve-like flaps in throat
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Inner Ear
• complex system of labyrinths
• osseous labyrinth
• bony canal in temporal
bone
• filled with perilymph
• membranous labyrinth
• tube within osseous
labyrinth
• filled with endolymph
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Inner Ear
Three Parts of Labyrinths
• cochlea
• functions in hearing
• semicircular canals
• functions in
equilibrium
• vestibule
• functions in
equilibrium
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Cochlea
Scala vestibuli
• upper compartment
• leads from oval window to
apex of spiral
• part of bony labyrinth
Scala tympani
• lower compartment
• extends from apex of the
cochlea to round window
• part of bony labyrinth
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Cochlea
Cochlear duct
• portion of membranous
labyrinth in cochlea
Vestibular membrane
• separates cochlear duct
from scala vestibuli
Basilar membrane
• separates cochlear duct
from scala tympani
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Organ of Corti
• group of hearing receptor cells
(hair cells)
• on upper surface of basilar
membrane
• different frequencies of vibration
move different parts of basilar
membrane
• particular sound frequencies cause
hairs of receptor cells to bend
• Ca influx causes NT release onto
sensory nerve
•AP generated-to medulla-to
thalamus-to auditory cortex
(temporal)
•Some crossover occurs
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Organ of Corti
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Auditory Nerve Pathways
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Summary of the Generation of
Sensory Impulses from the Ear
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Equilibrium
Static Equilibrium
• vestibule
• sense position of
head when body is
not moving
Dynamic Equilibrium
• semicircular canals
• sense rotation and
movement of head and
body
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Vestibule
• Utricle
• communicates with
saccule and
membranous portion of
semicircular canals
• Saccule
• communicates with
cochlear duct
• Mucula
• hair cells of utricle and
saccule
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Macula
• responds to
changes in head
position
• bending of hairs
results in generation
of nerve impulse
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Semicircular Canals
• three canals at right angles
• ampulla
• swelling of membranous
labyrinth that communicates
with the vestibule
• crista ampullaris
• sensory organ of ampulla
• hair cells and supporting
cells
• rapid turns of head or body
stimulate hair cells
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Crista Ampullaris
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